Driving connection for compound engines



w (No Model.)

H.D.D.UNBAR. DRIVING CONNECTION FOR COMPOUND ENGINES.

Patented Aug. 8,1893.

fave/11201."

UNITED STATES PATENT OFFICE.

HENRY D. DUNBAR, OF NORTH HARTLAND, VERMONT.

DRIVING CONNECTION FOR'CO'MPOUND ENGINES.

SPECIFICATION forming part of Letters Patent No. 502,956, dated August 8, 1893.

Application filed April 19,1893.

To all whom it may concern.

Be it known that I, HENRY D. DUNBAR, a citizen of the United States, and a resident of North I-Iartland, Windsor county, Vermont, have invented certain Improvements in Driving Connections for Oompound Engines, of

v which the following is a specification.

My invention relates to compound engines of that class in which the high and low pressure cylinders are located one above the other, both piston rods being connected to the same crank pin on the driving wheel, one object of my invention being to so connect the piston rods to the crank pin as to prevent such strains upon the guiding cross head as will cause the latter to wear unevenly, or such strains as will tend to cause fracture of the piston rods, and afurther object being to provide a connection whereby the dead point of the crank in its relation to one rod will be in advance of the dead point of the crank in its relation to the other rod. These objects I attain in the manner hereinafter set forth, reference being had to the accompanying drawings, in which- Figures 1 and 2, are diagrams illustrating the preferable method of carrying out my invention; and Figs. 3 and 4, are views illustrating certain modifications of the invention.

In Fig. 1, A and B represent, respectively, the high and low pressure cylinders of the engine, and a and b, respectively, the high and low pressure piston rods, the rod a being connected by a rod or, and the rod b, byarod b, to the crank pin d of the driving wheel, thecenter of which wheel is in a plane midway between the planes of the two piston rods. The outer end of the piston rod b is guided by a cross head f which is adapted to upper guides g of ordinary character, but the outer end of the piston rod a has no guided cross head, the maintenance of said outer end of the piston rod 0. in its proper vertical relation to the outer end of the piston rod 1) being insured by a spacing link or yoke 71 secured to both of the connecting rods a b at a point close to the points of attachment of said rods to the piston rods, the connections between the rods a b and link 71 being, by preference, rigid. The two connecting rods and the spacing link thus constitute a rigid triangular frame or truss having pivotal Serial No. 471,609. (No model.)

connection with the crank pin and with each piston rod, and as the crank pin is rotated, the swinging movement of this frame causes or permits one piston rod to move slightly faster than the other during part of the stroke, and correspondingly restricts its movement during the other part of its stroke, the pistons being in line with each other at each end of the stroke, a movement, however, which does not in any way interfere with proper operation of the engine. There is also a very slight vertical play of the piston rod 0. owing to the arc in whichits pivotal connection with the rod a swings, but this movementis readily permitted by the elastic packings of the piston and stuffing box and is without injurious results, while on the other hand the guidance of the two piston rods is effected without any more tendency to 'cause uneven wear of the cross head f than would exist in a single cylinder engine having its piston rod likewise guided.

Although I prefer to maintain the outer ends of the piston rods at the proper distance apart by means of the spacing link or yoke applied to the connecting rods, other means may be adopted for the purpose without departing from my invention. For instance, spacing links m connected to the ends of the piston rods may be employed as shown in Fig. 3, or the piston rod a may have a cross head 8 adapted to a guide n depending from and rigidly secured to the upper cross head f, this lower guide being of a length sufficient only to permit the differential movement of the two rods.

It will be seen that by reason of the use of the two connecting rods each piston rod transmits its force to the crank pin independently of the other rod; hence unequalpressure upon the pistons cannot cause any such strain upon the piston rods as will tendto fracture the same nor can it exert any strain upon the cross head tending to causeuneven wear of the latter. As the two piston rods, moreover,

occupy different relations tothe axis of the driving wheel it follows that the dead center point of the crank in its relation to one piston rod'is in advance of such point in its relation to the other rod; hence both connecting rods are never at the dead center at the same time and the power of one piston rod is therefore always exerted to move the crank pin over the dead center point of the other rod.

Having thus described my invention, I claim and desire to secure by Letters Patent l. The combination, in a compound engine 5 having superposed cylinders, of the two piston rods, two connecting rods, one for each piston rod, a guide for one of said rods, and 7 means for preserving the outer ends of the piston rods at the proper distance from each other without preventing independent longitudinal movement, substantially as specified. V

sozesc 2. The combination, in a compound engine having superposed cylinders, of the two piston rods, the two connecting rods one for each piston rod, a guide for one piston rod, and a spacing link or yoke uniting the two connecting rods, substantially as specified.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

HENRY D. DUNBAR.

Witnesses:

FRANK E. BECHTOLD, JOSEPH H. KLEIN. 

